A board unit which has a circuit board accommodated in a case is known in the art. In a board unit for vehicles, for example, an engagement structure for assembling a cover to the case utilizes engagement projections which are provided on lateral surfaces of the case, and engagement holes which are provided in lateral walls of the cover and engaged with the engagement projections, the lateral walls of the cover being arranged to overlap the lateral surfaces of the case (see JP 2005-151613A and JP 2006-275084A). Engagement between the engagement projections on the case and the engagement holes in the cover ensures engagement between the case and the cover in an assembled state.
A request for a board unit is to make sure that the cover is not detached from the case easily.
The above-mentioned engagement structure of the case and the cover relies on the engagement between the engagement projections and the engagement holes. If the cover is pressed from above, the lateral walls of the cover may deform outwardly in directions away from the lateral surfaces of the cover. Eventually, the engagement projections and the engagement holes may be disengaged from each other and may cause unnecessary detachment of the cover from the case. Once the cover is detached, components covered by the cover are exposed and cannot be properly protected by the cover.
Therefore, one of the objects of the present disclosure is to provide a board unit which can prevent unnecessary detachment of the cover from the case.